1. Field of the Invention
This invention relates to a control system for a stepper motor of the type which utilizes an analog signal to initiate rotation of the motor with the motor de-energized between moves.
2. Description of the Prior Art
Servo systems for positioning a mechanical element in proportion to an analog signal have been used in prior art but these have employed direct current motors instead of a stepper motor such as is employed in my invention.
A stepper motor typically has permanently magnetized poles arranged around the periphery of its rotor and a plurality of phase windings on its stator. The rotor advances from one pole to the next on each pulse which selectively energizes the stator windings.
Direct current motors have been proposed for positioning a mechanical element and usually employ a wound rotor connected to the driving source through a commutator, the stator providing a fixed magnetic field either through the use of permanent magnets or through electro-magnetic action.
Direct current motors have certain disadvantages in that they are larger than stepper motors for the same torque output, power must be applied to a direct current motor to lock the stator, and it is often difficult to precisely control the direct current motor rotation.